drivers/usb/core/notify.c

   1 /*
   2  * All the USB notify logic
   3  *
   4  * (C) Copyright 2005 Greg Kroah-Hartman <gregkh@suse.de>
   5  *
   6  * notifier functions originally based on those in kernel/sys.c
   7  * but fixed up to not be so broken.
   8  *
   9  */
  10
  11
  12 #include <linux/config.h>
  13 #include <linux/kernel.h>
  14 #include <linux/notifier.h>
  15 #ifdef CONFIG_USB_DEBUG
  16         #define DEBUG
  17 #else
  18         #undef DEBUG
  19 #endif
  20 #include <linux/usb.h>
  21
  22 #include "usb.h"
  23
  24
  25 static struct notifier_block *usb_notifier_list;
  26 static DECLARE_MUTEX(usb_notifier_lock);
  27
  28 static void usb_notifier_chain_register(struct notifier_block **list,
  29                                         struct notifier_block *n)
  30 {
  31         down(&usb_notifier_lock);
  32         while (*list) {
  33                 if (n->priority > (*list)->priority)
  34                         break;
  35                 list = &((*list)->next);
  36         }
  37         n->next = *list;
  38         *list = n;
  39         up(&usb_notifier_lock);
  40 }
  41
  42 static void usb_notifier_chain_unregister(struct notifier_block **nl,
  43                                    struct notifier_block *n)
  44 {
  45         down(&usb_notifier_lock);
  46         while ((*nl)!=NULL) {
  47                 if ((*nl)==n) {
  48                         *nl = n->next;
  49                         goto exit;
  50                 }
  51                 nl=&((*nl)->next);
  52         }
  53 exit:
  54         up(&usb_notifier_lock);
  55 }
  56
  57 static int usb_notifier_call_chain(struct notifier_block **n,
  58                                    unsigned long val, void *v)
  59 {
  60         int ret=NOTIFY_DONE;
  61         struct notifier_block *nb = *n;
  62
  63         down(&usb_notifier_lock);
  64         while (nb) {
  65                 ret = nb->notifier_call(nb,val,v);
  66                 if (ret&NOTIFY_STOP_MASK) {
  67                         goto exit;
  68                 }
  69                 nb = nb->next;
  70         }
  71 exit:
  72         up(&usb_notifier_lock);
  73         return ret;
  74 }
  75
  76 /**
  77  * usb_register_notify - register a notifier callback whenever a usb change happens
  78  * @nb: pointer to the notifier block for the callback events.
  79  *
  80  * These changes are either USB devices or busses being added or removed.
  81  */
  82 void usb_register_notify(struct notifier_block *nb)
  83 {
  84         usb_notifier_chain_register(&usb_notifier_list, nb);
  85 }
  86 EXPORT_SYMBOL_GPL(usb_register_notify);
  87
  88 /**
  89  * usb_unregister_notify - unregister a notifier callback
  90  * @nb: pointer to the notifier block for the callback events.
  91  *
  92  * usb_register_notifier() must have been previously called for this function
  93  * to work properly.
  94  */
  95 void usb_unregister_notify(struct notifier_block *nb)
  96 {
  97         usb_notifier_chain_unregister(&usb_notifier_list, nb);
  98 }
  99 EXPORT_SYMBOL_GPL(usb_unregister_notify);
 100
 101
 102 void usb_notify_add_device(struct usb_device *udev)
 103 {
 104         usb_notifier_call_chain(&usb_notifier_list, USB_DEVICE_ADD, udev);
 105 }
 106
 107 void usb_notify_remove_device(struct usb_device *udev)
 108 {
 109         usb_notifier_call_chain(&usb_notifier_list, USB_DEVICE_REMOVE, udev);
 110 }
 111
 112 void usb_notify_add_bus(struct usb_bus *ubus)
 113 {
 114         usb_notifier_call_chain(&usb_notifier_list, USB_BUS_ADD, ubus);
 115 }
 116
 117 void usb_notify_remove_bus(struct usb_bus *ubus)
 118 {
 119         usb_notifier_call_chain(&usb_notifier_list, USB_BUS_REMOVE, ubus);
 120 }